//** jQuery Scroll to Top Control script- (c) Dynamic Drive DHTML code library: http://www.dynamicdrive.com.
//** Available/ usage terms at http://www.dynamicdrive.com (March 30th, 09')
//** v1.1 (April 7th, 09'):
//** 1) Adds ability to scroll to an absolute position (from top of page) or specific element on the page instead.
//** 2) Fixes scroll animation not working in Opera.


var scrolltotop = {
  setting: {
    startline: 1,
    scrollto: 0,
    scrollduration: 80,
    fadeduration: [500, 100]
  },

  controlHTML: '<img src="http://my.oschina.net/img/gotop.gif" style="width:31px; height:31px;" />', //HTML for control, which is auto wrapped in DIV w/ ID="topcontrol"


  controlattrs: {
    offsetx: 100,
    offsety: 165
  }, //offset of control relative to right/ bottom of window corner
  anchorkeyword: '#top', //Enter href value of HTML anchors on the page that should also act as "Scroll Up" links

  state: {
    isvisible: false,
    shouldvisible: false
  },

  scrollup: function() {
    if (!this.cssfixedsupport) //if control is positioned using JavaScript
      this.$control.css({
        opacity: 0
      }) //hide control immediately after clicking it
    var dest = isNaN(this.setting.scrollto) ? this.setting.scrollto : parseInt(this.setting.scrollto)
    if (typeof dest == "string" && jQuery('#' + dest).length == 1) //check element set by string exists
      dest = jQuery('#' + dest).offset().top
    else
      dest = 0
    this.$body.animate({
      scrollTop: dest
    }, this.setting.scrollduration);
  },

  keepfixed: function() {
    var $window = jQuery(window)
    var controlx = $window.scrollLeft() + $window.width() - this.$control.width() - this.controlattrs.offsetx
    var controly = $window.scrollTop() + $window.height() - this.$control.height() - this.controlattrs.offsety
    this.$control.css({
      left: controlx + 'px',
      top: controly + 'px'
    })
  },

  togglecontrol: function() {
    var scrolltop = jQuery(window).scrollTop()
    if (!this.cssfixedsupport)
      this.keepfixed()
    this.state.shouldvisible = (scrolltop >= this.setting.startline) ? true : false
    if (this.state.shouldvisible && !this.state.isvisible) {
      this.$control.stop().show();
      this.state.isvisible = true
    } else if (this.state.shouldvisible == false && this.state.isvisible) {
      this.$control.stop().hide();
      this.state.isvisible = false
    }
  },
  offset: function(x, y) {
    scrolltotop.controlattrs.offsetx = x;
    scrolltotop.controlattrs.offsety = y;
  },
  init: function(userSetting, userControlHtml) {
    // custom setting
    scrolltotop.setting = $.extend(true, scrolltotop.setting, userSetting);
    scrolltotop.controlHTML = userControlHtml || scrolltotop.controlHTML;

    // original code
    jQuery(document).ready(function($) {
      var mainobj = scrolltotop
      var iebrws = document.all
      mainobj.cssfixedsupport = !iebrws || iebrws && document.compatMode == "CSS1Compat" && window.XMLHttpRequest //not IE or IE7+ browsers in standards mode
      mainobj.$body = (window.opera) ? (document.compatMode == "CSS1Compat" ? $('html') : $('body')) : $('html,body')
      mainobj.$control = $('<div id="topcontrol">' + mainobj.controlHTML + '</div>')
        .css({
          position: mainobj.cssfixedsupport ? 'fixed' : 'absolute',
          bottom: mainobj.controlattrs.offsety,
          right: mainobj.controlattrs.offsetx,
          display: 'none',
          cursor: 'pointer'
        })
        .attr({
          title: '回到顶部'
        })
        .click(function() {
          mainobj.scrollup();
          return false
        })
        .appendTo('body')
      if (document.all && !window.XMLHttpRequest && mainobj.$control.text() != '') //loose check for IE6 and below, plus whether control contains any text
        mainobj.$control.css({
          width: mainobj.$control.width()
        }) //IE6- seems to require an explicit width on a DIV containing text
      mainobj.togglecontrol()
      $('a[href="' + mainobj.anchorkeyword + '"]').click(function() {
        mainobj.scrollup()
        return false
      })
      $(window).bind('scroll resize', function(e) {
        mainobj.togglecontrol()
      })
    })
  }
};